Adhesively eradicable transfer medium

ABSTRACT

A TRANSFER MEDIUM OR TYPEWRITER RIBBON IS DISCLOSED WHICH IS CAPABLE OF BEING UTILIZED TO IMPRINT A LETTER AND IF THE LETTER IS ERRONEOUS, WHICH IS SUSCEPTIBLE OF ADHESIVE REMOVAL. THE RIBBON IS MADE OF A HARD, FILM FORMING RESIN WITH SELECTIVE MODIFICATION OF ITS PROPERTIES THROUGH THE ADDITION OF ADDITIVES WHICH EMBRITTLE THE FILM AND MAKE THE RESIN MORE ADHERENT FOR THE IMAGING SURFACE WHILE NOT PENETRATING INTO THE FIBERS OF THE PAPER FIBERS IMAGING SURFACE, AND ATTACHING ITSELF. AS TIME PASSES THERE IS AN INCREASED ATTACHMENT TO THE PAPER FIBERS THEREBY RENDERING A MORE PERMANENT IMAGE. THE RIBBON IS FORMED FROM A SOLVENT BLEND OF RELATIVELY HIGH PROPORTIONS OF TOLUENE AND CORRESPONDINGLY REDUCED ISOPROPANOL.

United States Patent O 3,825,437 ADHESIVELY ERADICABLE TRANSFER MEDIUM Samuel Darrell Blair, Lexington, Ky., assignor to International Business Machines Corporation, Armonk, N.Y. N Drawing. Filed Aug. 3, 1972, Ser. No. 277,543 Int. Cl. B41c 1/06 U.S. Cl. 11736.1 4 Claims ABSTRACT OF THE DISCLOSURE A transfer medium or typewriter ribbon is disclosed, which is capable of being utilized to imprint a letter and if the letter is erroneous, which is susceptible of adhesive removal. The ribbon is made of a hard, film forming resin with selective modification of its properties through the addition of additives which embn'ttle the film and make the resin more adherent for the imaging surface while not penetrating into the fibers of the paper imaging surface, and attaching itself. As time passes there is an increased attachment to the paper fibers thereby rendering a more permanent image. The ribbon is formed from a solvent blend of relatively high proportions of toluene and correspondingly reduced isopropanol.

RELATING C'OPENDING APPLICATIONS This invention is an improvement of the invention disclosed and claimed in U.S. Patent Application Ser. No. 277,696 cofiled with this application in the name of Donald L. Elbert, et al., entitled Adhesively Eradicable Transfer Medium.

BACKGROUND OF THE INVENTION This invention relates to transfer mediums and more specifically to an improved typewriter ribbon.

Typewriting errors have occurred since the first typewriter was invented. The problem has been addressed in many ways including the development of an erasable bond paper which allows the erroneous letters to be manually erased using a normal pencil or typewriter eraser of a rubber or combination rubber and abrasive material. Other more recent techniques for correcting typewriting errors have included covering the erroneous letter or symbol to camouflage its appearance to give the general appearance of no error having been made. This is accomplished through one of several techniques. One tech nique which has been used is a liquid which contains a pigment or pigmented material carried in a volatile carrier fluid. This correction material is painted over the erroneous letter and allowed to dry thus adhering to the image sheet and providing a relatively unobtrusive correction. An alternate technique which has been used is that of a dry transfer material for covering the erroneous letter. The material is usually formed into a thin layer on a film or carrier sheet much the same as carbon paper and then used together with the impact of the erroneous letter to transfer a thin white layer or layer of other desired color onto the surface of the erroneous letter thus partially if not completely obscuring it from view.

There have in the past been disclosures relating to the correction of errors on a typewriter by use of an adhesive tape or adhesive material but the technique used resulted in the disruption of the surface of the image sheet in that fibers from the paper were literally pulled out of the sheet in order to adequately remove the erroneous image. This is required because the ink of the ribbons at that time had the capability of penetrating into the paper fibers and staining or permanently dyeing the paper upon printing and the fibers had to be physically removed from the surface of the paper to remove the image.

BRIEF DESCRIPTION OF THE INVENTION The transfer medium, hereafter interchangeably referred to by ribbon or typewriter ribbon, is constructed using the residue of a solvent blend coated mixture to form a transfer layer, also referred to as the ink or ink layer. The ink layer is deposited upon a flexible thin supporting substrate. The solvent blend coated residue coating which makes up the ink is preferably formulated from a film forming resin which is hard rather than a waxy or friable resin and which is made brittle or frangible by the addition of a modifying agent, without softening the resin substantially. A second modifying material is added, if required, to make the ink layer releasable from the support substrate or film but yet still have a relatively high tendency to adhere to paper. The resin is preferably not substantially softened as softening will enhance smearing and smudging and promote adherence to the image sheet, resulting in poor error correction. The need for additives to increase edge definition and prevent detrimental effects of some of the necessary modifying materials, is obviated by the use of a solvent blend as described herein.

Correction of erroneously typed letters or symbols may be accomplished by adhesive removed from the surface of the image sheet or paper, using a piece of material having an adhesive surface, where the adhesive surface is impacted onto the erroneously typed letter. This adheres the adhesive surface of the correction material to the letter and when the correction material is pulled from the paper it pulls the letter with it. The resin used in the formulation of the ink layer as modified, must be cohesive to the point that it will hold the ink layer together for removal and not crumble, since the adhesive surface of the correction material is only in contact with one surface of the ink layer. If the resin has insufficient cohesive effect, only the exposed portion of the erroneous letter is removed and remainder of the image ink layer continues to adhere to the image sheet and thus leave a residue image. The cohesion of the ink layer must be greater than the ink layers atfinity for the paper or image surface. The ink layer must be formulated so that the adhesion is one of surface adhesion between the ink and the paper rather than a viscous penetration of the paper fibers or wetting of the paper fibers with the ink layer. Preferably no dyes are used in the coloring of the ink layer as dyes generally have a staining capability and stains and staining are to be avoided. Dyes mean only colorants which are soluble in the other components of the ink mixtures.

The ink layer is deposited from a relatively high toluene loaded solvent blend of toluene and isopropanol to control the adverse effects of modifying agents While not reducing their desirable properties, and the adhesive correction materials which have been found to perform most advantageously are substrates preferably polyethylene terephthalate, which have been coated with a rubber or acrylic base adhesive. Generally speaking, silicone adhesive base materials appear to be only marginally operative or operative only on selected papers. Unless the adhesive attraction for the ink exceeds that of the ink for the paper, only partial removal of the erroneous character will occur.

OBI ECT S OF THE INVENTION It is the primary object of this invention to improve the imaging of symbols and characters on an image sheet and that at the same time are readily correctable by impacting adhesive material into intimate contact with the letters or images.

It is another object of this invention to complement automatic erase or correction typewriting apparatuses with an improved adhesively correctable typewriter ribbon.

It is an additional object of this invention to reduce the humidity sensitivity of the ribbon during manufacture and eliminate heretofore utilized constituents.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION The following explanation of the function of particular materials represents what is believed to be the best explanation in as much as the complete interaction is not fully understood.

The ink layer of the transfer medium or ribbon is compounded from carefully selected materials which provide the unique quality of being substantially, completely, adhesively removable from the image sheet onto which the ink has been transferred in the process of typewriting. The characteristics of the materials which are necessary to formulate a ribbon of the adhesively removable type are explained to the best of the understanding as it presently exists.

The primary constituent of the ink or ink layer of the correctable ribbon is a resin. The resin must be a hard resin rather than a waxy resin. Additionally, the resin must be of the type which is capable of solution in a solvent in order that the ink formulation may be deposited in a solution/dispersion form in a volatile carrier liquid.

To obtain the necessary cohesion in the ink layer it has been found that the resin should be of the film forming type which has a high degree of flexible integrity and is not so friable or flaky that it will flake or crumble similar to a wax. To obtain the necessary adhesion between the pressure sensitive adhesive and the ink, the resin must be readily wetted by most materials used to make pressure sensitive adhesive, i.e. rubbers and acrylics.

The resin preferably is of the form which although in contact with paper and paper fibers does not penetrate into the surface of the paper. This characteristic is important in that it allows the relatively easy removal of an erroneously typed letter.

The resin functions as the carrier, holder, or binder for other constituents of the ink layer.

Typical resins which possess the above properties are enumerated in the above referenced Elbert, et al. application.

The preferred resin is Ernerez 33 marketed by Emery Industries. Emerez 1533 is believed to be a diphenolic based polyamide having a softening point of about 98 to 102 C., viscosity at 160 C. of 26 to 34 poise, and an amine value of 5.2 milligrams KOH per gram and an acid value of 2.5 milligrams KOH per gram. Emerez 1533 also has a density of 8.3 pounds per gallon.

To modify any of the foregoing resins to provide them with an ultimate physical characteristic which is desirable, that of reduced tensile strength or film integrity, additives are included in the ink layer formulation.

To render the resin adequately frangible or brittle to provide sharp character definition upon impact by the type font, it is necessary to lower the tensile strength of the film formed by the resin when deposited from a solvent. It is desirable to avoid excessive softening of the resin as softening will make the resin more waxy or waxlike and reduce its removeability from the paper surface. The weakening of the tensile strength or lowering of the tensile strength of the film formed by the resin appears to be as a result of the additive reducing the tendency for the polymer chains of the resin to intertangle. This reduced intertangling of the molecular chains in the resin reduces the film forming characteristic to the point where the film will break easily as compared to its unmodified state. The preferred modifying agent for reducing the tensile strength of the resin is a mineral oil. Mineral oils may be selected within a relatively 'wide range of viscosities and properties to accomplish the degree of modification necessary with each individual resin. A preferred mineral oil is Standard #34 'Kyso white mineral oil sold by Standard Oil Company of Kentucky.

A second modifying agent is generally necessary to cause the ink layer to be less adherent with respect to the support substrate or film material upon which the ink layer is deposited to form the transfer medium. Generally such a film is a polyethylene film, but may be any other common film used in ribbon manufacture.

Preferably, the release properties may be imparted to the ink mixture by the addition during formulation of mixed octyl esters of fatty acids. One example of the appropriate esters which may be used to act as a release agent is a material marketed under the tradename Plasticizer R9C 7025 by the 'C. P. Hall Company of Chicago, Ill. The Plasticizer R9C 7025 acts as a plas ticizer in the more classic sense, in that it modifies the resin material such that it has an adherence to the paper which is enhanced but is not such that the adherence for the paper is so great that the images cannot be removed by being strongly contacted on the exposed surface by an adhesive coated substrate. Other known modifying agents include fatty acid esters type of plasticizers such as isopropyl palmitate and butyl stearate. These other agents react similarly to the Plasticizer R9C 7025.

In all formulations it is necessary to provide a coloring agent if the transferred ink layer is to be visible in contrast to the paper background. The preferred material for providing color includes carbon black. Other alternative materials, of course, would be different colored pigments which are not soluble in the modifying oils selected. Organic dyes may be used as pigments if they are insoluble in the modifying oils.

Humidity has been shown to be a strongly influencing factor in the manufacture of the adhesively correctable ribbon. The effect that humidity plays is not fully understood but is believed to be an effect on the film structure of the film forming resin as it is deposited from the solvent vehicle, while being dried, to form the ink transfer layer. It has been found that if the humidity is too high or too low, the eradication of the printed character is incomplete and unacceptable. It is believed that due to the evaporation of the solvent of the ink formulation,

the temperature of the web when coated with the ink mixture is reduced to the point that a small quantity of moisture from the atmosphere condenses on the surface of the ribbon as it is being dried of the solvent mixture. The formation of the water droplets or moisture pockets on the surface of the ink layer are believed to affect the formation of a discontinuous film and also to effect the manner in which the materials of the ink formulation are deposited. Acceptable eradication results occur when the humidity in the manuftcturing area is such that the film is coated with the ink mixture and then exposed to air containing from about .005 to about .012 pounds of.

limits of toluene could be tolerated. The toluene acts to force the mineral oil into solution which does not occur in a straight isopropanol system. The increase of toluene was believed to be detrimental but proved to favorably effect the humidity sensitivity of the ink layer. By using a solvent blend as herein disclosed, the removal of components functioning as edge definition sharpeners and oil migration preventors, is permitted.

Examples For the sake of simplicity in understanding the disclosure, a complete step by step preparation procedure for one formulation will be described with the understanding that the other formulations are prepared in the same or an analogous manner using designated substituted materials, varied quantities, or substituted solvents. All constituents will be listed together with a percentage which represents the percentage of that constituent of the entire dry ink mixture or dry ink layer. The materials will be compounded in an analogous manner to that of the first example with adjustments being made with respect to quantities and proportionate amounts of solvents.

EXAMPLE 1 Number of parts I Perby Solids centage weight Resin (Emerez 1533) 28. 6 30 Mineral oil (Standard 34 Kyso white mineral 23. 8 25 Plasticizer (plasticizer R9C 7025)... 10 Pigment (Mogul L) 28. 6

.and filtered. A solvent blend having a solvent ratio of 3.4 parts isopropanol to one part toluene is prepared. To five parts of the above solvent blend, one part of Plasticizer R-9C 7025 and 1.25 parts of Standard #34 mineral oil is added and thoroughly mixed. To this mixture 7.5 parts of the above dispersion and 11.5 parts of the solvent blend are added with stirring. This resulting mixture is then coated onto a substrate, preferably a three quarter mil polyethylene high density film. The mixture is coated at F. to 100 F., preferably at room temperature and to a coat weight of approximately 1.0 to 1.4 pounds per ream and dried in a dryer at a temperature of from approximately 100 F. to 140 F. Humidity is maintained at from about .006 to about .009 pounds of water per pound of dry air during the coating and drying operation.

Following the above procedure a ratio of toluene to isopropanol in the coating solution of about 1:4 is realized. This ratio is highly advantageous. Reasonably acceptable results are possible with a percentage range of 20% toluene and isopropanol with a tolerance of :5%, all percentages on solvents being as a whole of the solvent content of the ink as ready to coat.

In the removal of letters imprinted by the impact of a type font with the above formulated transfer medium, it has been found that there are several adhesive tapes which are particularly useful. Adhesive tapes designated by the designation Y9272 and 853 and 351 are available from the Minnesota Mining and Manufacturing Company. A product designated by product #7321 is available from Borden Company and adhesive tape designated by a product #440 is available from Nashua Corporation, Nashua, New Hampshire.

While the invention has been particularly described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An improved adhesively correctable transfer medium of the complete transfer type comprising:

a thin flexible film substrate;

an ink layer of the complete transfer type coated there said complete transfer ink layer consisting essentially of the dry residue of a solvent blend coated solution/ dispersion; said solution/dispersion comprising,

about 28 to 32 parts of a resin of the hard, nonwaxy film forming type polyamide resin, about 23 to 27 parts of a mineral oil, mixed with and embrittling said resin for fracture, about 18 to 22 parts of a mixed octyl ester of fatty acids plasticizer, for adding adhesion properties for an imaged surface and for enhancing release from said substrate, about 28 to 32 parts of a pigment, said pigment dispersed throughout said resin, oil and fatty acid esters, about 320 to 350 parts of isopropanol, and about 80 to parts of toluene. 2. The transfer medium of Claim 1 wherein said pigment is carbon black.

3. An improved method of making an adhesively eradicable transfer medium of the complete transfer type, comprising the steps of:

preparing an approximately 15 to 25% non-volatiles solution/dispersion of 28-32 parts hard non-waxy film forming polyamide resin, 23-27 parts mineral oil, 18-22 parts mixed octyl esters of fatty acids plasticizer, and 28-32 parts pigment in a solvent blend having a ratio of approximately 1.4 toluene to isopropanol, all parts being by weight,

providing a thin flexible substrate, and coating said solution/ dispersion on said substrate,

drying said solvents from said coating in an atmosphere having a water content of from about .005 to .012 pound of water/pound of dry air and a temperature of from about F. to about F., thereby forming an adhesively eradicable transfer medium.

4. The process of Claim 3 wherein said Water content is from about .006 to about .009 pounds of water per pound of dry air.

References Cited UNITED STATES PATENTS 3,682,683 8/1972 Elbert et al. 117--36.1 3,350,205 10/1967 Gotfe 117-36.7 3,384,504 5/1968 Ernst 11736.7

MICHAEL SOFOCLEOUS, Primary Examiner US. Cl. X.R. 1l7138.8 R, E

Po-ww UNITED STATES PATENT, OFFICE [6'54 (5 CERTIFICATE OF CORRECTION Patent No. 3,825,437 Dated Au ust 7. 1974 Inventofls) Samuel Darrell Blair It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Specification:

Column 1, line 26 delete "RELATING" and insert "RELATED" Column 4, line 53 delete "manuftcturing" and insert --manuacturing-- In the Claims Column 6 line 40 delete "1.4" and insert --1:4-.

Signed and sealed this 5th day of November 1974.

(SEAL) Attestz McCOII' M. GIBSQN JR. C. MARSHALL DANN Attestin Officer Commissioner of- Patents 

